Those radials are just conductors of the proper length for the frequency of the antenna. They can be made from almost anything conductive. If you have a few Francis antennas and want to use them, have at it. Common aluminum tubing would work just as well.
Painting. If the paint isn't conductive it shouldn't make any difference at all.
- 'Doc
(Hot Pink works exceptionally well, I think!)
Should have added this, just forgot, sorry 'bout that.
You will probably have to do some 'tunning' of those Francis whip radials. No idea how difficult that would be. It will probably make them unusable for antennas without reversing that 'tunning' thingy. If they are 'trash' to start with you haven't lost anything. If they are still usable, I'm not too sure I'd do it. Up to you...